JPH037852B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a device for detecting boiling of water in a container placed on a heat appliance such as an electric stove.

BACKGROUND TECHNOLOGY Conventionally, a boiling detection device used in an electric stove, etc. has a temperature sensor that can be moved in and out of the center of a sheathed heater formed in a spiral shape, and the temperature sensor measures the temperature of a container containing water. Based on the correlation between the temperature of the water and the temperature of the temperature detector, the temperature of the temperature detector when the water boils is detected and the power supply to the heater is stopped. If the contact between the container and the temperature sensor deteriorates due to fruit, dirt, etc., the temperature sensor will be affected by the radiant heat of the heater rather than the temperature transferred from the container, and the temperature will reach the temperature before boiling. It started working and sometimes stopped heating. In addition, taking into consideration factors such as a decrease in the boiling point due to atmospheric pressure and variations in the operating temperature of the temperature detector,
The boiling detection point had to be set at around 90°C to 95°C. In other words, it was not possible to detect the completion of boiling at 100°C (at normal pressure).

As a way to compensate for these shortcomings of conventional temperature detection devices, there is a method that detects the change in temperature rise of the temperature detector before and after boiling of water as a change in temperature rise rate or temperature gradient, and detects the boiling point. ing. According to this method, it is possible to detect boiling of water, and it is also possible to detect boiling in response to a decrease in the boiling point due to atmospheric pressure.

Problems to be Solved by the Invention However, even with this method, if the thermal coupling between the temperature sensor and the container is poor, detection of changes in the temperature rise rate or temperature gradient will be delayed, and heating will continue even after boiling. However, there is a problem that power is wasted. In addition, if oil, etc. is placed in the container, there is no change in the temperature rise rate or temperature gradient, so detection is impossible and the heater cannot be controlled. As a result, when heating continues, the oil There was also the problem of creating a dangerous situation that could lead to smoke and ignition.

An object of the present invention is to provide a boiling detection device that solves these problems.

Means for Solving the Problems In order to solve the above problems, the present invention provides a heating element that heats a water storage container, a temperature detector that detects the temperature of the container, and a temperature sensor that detects the temperature of the container. Temperature increase rate measuring means for measuring the temperature increase rate of the temperature detector using temperature as an input signal; and temperature determination means for determining that the temperature of the temperature detector is higher than a set temperature using the temperature detected by the temperature detector as an input signal. and boiling determining means that uses the output of the temperature increase rate measuring means as an input signal and determines that the water in the container has boiled when the temperature decreases below a predetermined temperature increase rate;
heating element energization control means for controlling energization of the heating element based on the output of the boiling determination means or the output of the temperature determination stage; Under good conditions, the output of the boiling determination means will stop the energization of the heating element, and under conditions of poor thermal coupling between the container and the temperature sensor, the output of the temperature determination means will stop the energization of the heating element. Further, the set temperature at which the temperature determination means outputs an output is set higher than a temperature corresponding to a bending point at which the rate of temperature rise changes in a state where the thermal coupling between the container and the temperature sensor is poor. It is something.

Effect According to the above configuration, the temperature rise rate of the temperature sensor that detects the temperature of the container containing water is continuously measured, and if the thermal coupling state between the container and the temperature sensor is good, the water is heated after boiling. The power supply to the heating element is controlled when the temperature rise rate of the temperature sensor falls below a predetermined value, and it also prevents dirt or foreign matter from adhering between the container and the temperature sensor, causing thermal coupling between the two. Worse, the temperature rise rate of the temperature sensor may continue even after boiling without dropping below the specified temperature rise rate, or there may be a change in the temperature rise rate of the temperature sensor due to oil, etc. being placed in the container. If the heating continues without the oil being turned off, the power supply to the heating element is controlled when the temperature detected by the temperature sensor reaches a predetermined temperature or higher, thereby reducing wasteful power consumption, overheating of the oil, and so on.
Furthermore, it is possible to prevent dangers such as ignition.

Embodiment Hereinafter, an electric stove as an embodiment of the present invention will be described. In FIG. 1, 1 is an AC power supply, and a capacitor 2 connected to this AC power supply 1,
The resistor 3, Zener diode 4, resistor 5, and diode 6 form a DC power source for operating the control circuit. Reference numeral 7 denotes a container for containing water, which is removably placed on the heating element 8. The heating element 8 is formed of a spiral sheathed heater. Reference numeral 9 denotes a three-terminal bidirectional thyristor connected to the heating element 8 and serving as heating element energization control means. When this three-terminal bidirectional thyristor 9 is turned on, the heating element 8 generates heat, and the container 7
heat up. A thermistor 10 is a temperature detector, and is thermally coupled to the lower side of the container 7 so as to be detachable. The temperature detector 10 may be provided at the center of the heating element 8 so as to be vertically retractable, and may be thermally coupled to the outer bottom surface of the container 7 so as to be able to come into contact with and separate from it. The control circuit is composed of a microcomputer 11 and peripheral circuits.
1 is a so-called one-chip microcomputer consisting of a CPU, ROM, RAM, and input/output ports. A start switch 12 is connected to the input port of the microcomputer 11, and is connected to the input port of the microcomputer 11 through a closed circuit.
The transistor 13 connected to the output port 1 is driven, and the heating element energization control means 9 is energized. 14 is an A/D converter which converts the analog signal of the temperature detector 10 into a digital signal and outputs it to the computer 11. 15 is a light emitting diode constituting the boiling alarm means, and the microcomputer 11
connected to the output port of the

Next, the operation of the boiling detection device having the above configuration will be explained. Pour water into container 7 and press start switch 1.
2 closes, the microcomputer 11
Temperature detection is started based on the program procedure shown in the flowchart of FIG. 3 stored in the ROM.

First, in a step, the heating element 8 is energized, and the container 7 is heated.
is heated, and a step (temperature determining means) determines whether the temperature of the temperature detector 10 is higher than a predetermined temperature. If the temperature has not reached that temperature, a step (temperature increase rate measuring means) determines the temperature increase rate. is measured and compared in step to see if it is below a predetermined temperature increase rate, and if it is above the predetermined temperature increase rate, returns to step and determines whether the temperature of the temperature detector 10 is above the predetermined temperature, If the predetermined temperature has not been reached, step 2 is repeated and the rate of temperature rise is continuously measured. If the temperature rise rate falls below a predetermined rate in the step, it is determined that the boiling has occurred in the step (boiling determination means), the light emitting diode 15, which is the boiling alarm means, is turned on in step 6, and the power to the heating element 8 is turned off in step 6. Stop and complete boil detection operation. The above program flow shows the detection of boiling water in the container 7 and the control of the heat generation 8 when the thermal coupling between the container 7 and the temperature sensor 10 is good. 10
The following describes the program flow when there is dirt or foreign matter between the two and the thermal coupling between the two is poor, or when oil is placed in the container and temperature cannot be detected.

When the start switch 12 is closed, the heating element 8 is energized in step to heat the container 7, and in step it is determined whether the temperature of the temperature detector 10 is above a predetermined temperature. , step measures the temperature increase rate, and compares whether the temperature increase rate is below a predetermined temperature increase rate in step, and if the temperature increase rate is above, returns to step and determines whether the temperature of the temperature detector 10 is above the predetermined temperature, If the predetermined temperature has not been reached, repeat the steps.
Repeat this to continuously determine the temperature rise rate. The flow up to this point is the container 7 and temperature sensor 1 described above.
This is the same as when the thermal coupling with 0 is good. By the way, if the thermal coupling described above is poor, even if the water starts to boil, the temperature sensor 10 will be heated due to the radiant heat of the heating element 8.
The temperature rise rate of does not fall below a predetermined value, which will be described later.
As a result, the heating element 8 continues heating by repeating steps . As the heating element 8 continues to heat, the temperature of the temperature detector 10 increases, and as will be described later, the temperature reaches a predetermined temperature or higher. At this time, the program moves from step to step, and the power supply to the heating element 8 is stopped. Similarly, when oil is placed in the container 7, the temperature rise rate of the temperature detector 10 will not fall below a predetermined value, and the steps .
The process is repeated until the temperature of the temperature detector 10 reaches a predetermined temperature or higher, and as the process moves from step to step, the power supply to the heating element 8 is stopped.

Next, the predetermined temperature increase rate and predetermined temperature of the above-mentioned temperature detector will be explained with reference to FIG.
In the figure, A indicates the water temperature in the container, B indicates the temperature of the temperature detector 10 when the thermal coupling with the container 7 is good, and C indicates the temperature of the temperature detector 10 when the thermal coupling is poor. There is. As described above, the temperature detector 10 is provided so as to be thermally coupled to the lower part of the outer surface of the container 7 or the outer bottom surface so as to be able to come into contact with and be separated from the container 7, and mainly detects the temperature of the container 7. It is easily understood that due to the structure of the electric stove, the temperature will be higher than that of the container 7 due to the radiant heat of the heating element 8. Therefore, as shown in the figure, the temperature of the water in the container 7 rises faster than A, but if the thermal coupling is good, there is a correlation between the two, and the water temperature increases until the water boils. The temperature rises almost parallel to .
Eventually, when the water starts to boil, the temperature of the temperature detector 10 also exceeds 100 degrees Celsius and becomes a nearly constant temperature.
The temperature rises little by little over time due to the radiant heat of the heating element 8. The temperature rise per unit time in this state is defined as the temperature rise rate, and a value unique to the device is set as the predetermined temperature rise rate of the temperature detector 10. However, if the thermal coupling between the container 7 and the temperature detector 10 is poor, the temperature correlation between the two will collapse.
The temperature sensor 10 is more influenced by the temperature due to the radiant heat of the heating element 8 than when the thermal coupling is good, and the temperature rises much faster than the water temperature rises. Then, when the water boils (A), it bends a little later (B)
However, even after that, the temperature increases at a higher rate than the predetermined rate of increase in temperature when the thermal coupling is good.

Here, the relationship with the operation of the steps in the flowchart of FIG. 3 will be explained. Temperature detector 1
As mentioned above, the temperature at 0 follows the course of B or C in Figure 2, but in this case, the rate of temperature increase while the water temperature is rising is greater than the predetermined rate of temperature increase, so steps , , etc. are repeated. . This repetition is the same whether the thermal coupling between the container 7 and the temperature sensor 10 is good or bad. Eventually, when the water starts to boil, the temperature sensor 10 will react if there is good thermal coupling.
The temperature is almost constant or slightly rising (second
When the temperature rise rate becomes lower than the predetermined temperature rise rate set in advance, the process moves on to step 2, and it is determined that the water has boiled.

On the other hand, if the thermal coupling is poor, the temperature of the temperature sensor 10 will rise even after the water boils (Fig. 2 (c)), and the temperature rise rate will exceed the predetermined temperature rise rate, so the process returns to step Heating by the heating element 8 is continued by repeating . In addition, when oil is put in the container 7, there is of course no inflection point of the temperature of the temperature sensor 10 at the time corresponding to the boiling of water. Therefore, the temperature rise rate does not fall below a predetermined temperature increase rate, and heating by the heating element 8 continues.

Next, the predetermined temperature will be explained. As mentioned above, if the thermal coupling between the container 7 and the temperature sensor 10 is poor or if the container 7 is filled with oil,
Since heating by the heating element 8 continues without determining boiling, there is a risk of wasteful power consumption and oil ignition. To deal with these problems, it is most desirable to forcibly stop the power supply to the heating element 8, and for this purpose, the step is made to shift from step to step when the temperature detector 10 reaches a certain temperature or higher. The temperature is a predetermined temperature C of the temperature detector 10, and when the thermal coupling between the container 7 and the temperature detector 10 is good, the temperature is higher than the temperature B of the temperature detector 10 which shows a stable temperature course after boiling of the water. is set to a value unique to the device (in the example of FIG. 2, a temperature slightly higher than the bending point B of the temperature C of the temperature sensor when thermal coupling is poor).

Here, the relationship with the operation of the steps in the flowchart of FIG. 3 will be explained. When the thermal coupling between the container 7 and the temperature sensor 10 is good, the temperature of the temperature sensor 10 follows the course shown in Fig. 2 (b), so the temperature never exceeds the predetermined temperature, and steps . Repeatedly, as the water boils, the process moves from step to step and boiling is determined. On the other hand, if the thermal coupling is poor, the temperature of the temperature detector 10 follows the course shown in Fig. 2C while repeating steps , and reaches the predetermined temperature C. When the temperature exceeds the predetermined temperature, , the process moves from step to step and the power supply to the heating element 8 is stopped. Similarly, when oil is placed in the container, when the temperature of the temperature detector 10 reaches a predetermined temperature C or higher, the process moves from step to step, and the power supply to the heating element 8 is stopped.

As described above, in the boiling detection device according to the embodiment of the present invention, the temperature rise of the temperature sensor 10 is correlated with the temperature rise of the water, and in particular, after the water boils, the thermal relationship between the container 7 and the temperature sensor 10 is Focusing on the fact that there is a difference in the temperature rise rate of the temperature sensor 10 depending on the quality of the bond, if the temperature rise rate of the temperature sensor 10 after boiling is below a predetermined temperature rise rate, that is, thermal bond If the temperature rise rate is good, it is determined that boiling has occurred, and the power supply to the heating element 8 is stopped. By controlling the electricity supply to the heating element 8 to be stopped when the temperature exceeds , it is possible to eliminate boiling detection and wasteful power consumption.

Furthermore, by controlling the power supply to the heating element 8 to be stopped when the temperature of the temperature detector 10 reaches a predetermined temperature or higher, even when oil is contained in the container 7, the oil can be removed. It is possible to prevent overheating of the product, and to prevent dangers such as smoke and ignition. This effect of preventing overheating of the oil in the container 7 is utilized as follows. BACKGROUND ART In recent years, in order to rationalize housework functions, heating devices for cooking that have a plurality of heating parts and have a large heat capacity, such as the so-called electric range type, have come to be used. In order to use such a heater in an energy-saving manner or as an optimal cooking device, it is desired to save power in the frequently used water boiler and automatically control the cooking device. Therefore, if we focus on the fact that an electric range has multiple heating parts as mentioned above, one of the multiple heating parts is equipped with a boiling detection device for boiling water, and the other one is equipped with an automatic control device for frying food. The device can be installed to save power and improve functionality. By the way, in actual use, a container containing oil for frying is sometimes placed on the heating section of a water boiler, and in this case, the oil temperature cannot be automatically controlled, so there is a risk of smoke or ignition. It is practical and safe to stop heating until the end of the process. In such cases, the boiling detection device of the present invention can accurately detect boiling and stop heating in the case of boiling water, and stop heating in the case of oil heating. This device can be effectively used as a power saving and danger prevention device.

Note that it goes without saying that stopping the energization to the heating element upon detection of boiling may be done by controlling the amount of energization to the heating element, and keeping the hot water warm after boiling.

Effects of the Invention As is clear from the description of the above embodiments, the boiling detection device of the present invention detects boiling and controls energization to the heating element regardless of whether the thermal coupling between the container and the temperature sensor is good or not. This makes it possible to save power on heating equipment, and when heating oil for frying, etc., it is possible to control the current to the heating element during heating to prevent dangers such as smoke and ignition. In addition, it can be used in heating equipment having multiple heating parts to save power and ensure safety.

[Brief explanation of the drawing]

Fig. 1 is an electric circuit diagram of a boiling detection device showing an embodiment of the present invention, Fig. 2 is a temperature characteristic diagram of the main parts, and Fig. 3 is an example of a program for boiling detection of the same boiling detection device. This is a flowchart. 7... Container, 8... Heating element, 9... Heating element energization control means, 10... Temperature detector, 11... Microcomputer, 15... Boiling alarm means.

Claims (1)

[Claims] 1. A heating element that heats a water storage container, a temperature detector that detects the temperature of the container, and a temperature rise rate measurement that measures the temperature rise rate of the temperature sensor using the temperature detected by the temperature detector as an input signal. a temperature determining means that uses the temperature detected by the temperature detector as an input signal to determine that the temperature is higher than a set temperature; a boiling determination means for determining that the water in the container has boiled when the water reaches a temperature below the boiling point; and a heating element energization control means for controlling energization to the heating element based on the output of the boiling determination means or the output of the temperature determination means. The heating element energization control means stops the energization of the heating element by the output of the boiling determination means when the thermal coupling between the container and the temperature sensor is good, and the heating element energization control means Under conditions of poor thermal coupling between the container and the temperature detector, the output of the temperature determining means is used to stop the energization of the heating element. A boiling detection device characterized in that the rate of temperature rise in a state of poor coupling is higher than the temperature corresponding to the bending point at which the bending changes.